Ground-connector.



J. L. DONALD. GROUND CONNECTOR. APPLIOATIOH rmm mm. 19, 1908.

Patented Sept. 20, 1919'.

cuit branches and connections.

JAMES L. DONALD, OF MOORESVILLE, NORTH CAROLINA.

osouun-oon'nncron.

Specification of Letters Patent.

Application filed December 19, 1908.

Serial n6. 3

"i atented Sept. 20, 1910.

see, as.

Ground-Connectors, of which the followingis a full, clear, and exactdescription.

My invention relates to a ground connector, particularly for use inconduit wiring.

"it isa usual practice to run the circuit wires for lamps, motors andother electrical appliances through -'conduits of ordinary iron piping,interrupted at intervals by the switch, outlet and junction boxes forthecir- .The main object of this arrangement is to provide ah soluteprotection against fire, it being evident that any grounds orshort-circuite n the circuit wires can do no damage if they are entirelyinclosedin a wrought iron pipe. But in order to make the protection complete and adequate, it is evident that the pipev must be thoroughlygrounded at all points, so that grounds or short-circuits from theinterior circuit Wires or from any exterior conductor, will notelectrify a portion of the length or the pipe to a sparking or arcingpotential by reason of any poor or inadequate ground connection of suchpipe section. it IS evident thatsonie means must be provided forinsuring a low resistance path to ground from every portion of theconduit pipe, in case the latter is to.be any real protection againstfire a; l. other damage, due to grounds or short-circuits of theinterior circuit wires, or any exterior charged conductor. J l V g It sthe purpose oi my invention to provide a very simple and eliicient meansfor this urpose/ i 1th this object in view, my invention consists in thefeatures of construction and combination as hereinafter set. forth andclaimed.

In the drawings: Figure 1 is a view'showing the general features of anordinary conduit wiring system embodying the principles of my invention;liig. 2 is a perspective view (if one of the grounding applizinc-es, andFig. 3 is a detail sectional View of the same.

Referring to the drawings: 1 designates sections or portions of anordinary conduit, pipe, and Qdenotes an outlet, switch or.

junction box of the type ordniamyflenr ployed and to which the pipesections 1 aret'hreaded, either directly or through any iuteriuediutebushings (not shown). The boxes are ordinarily made of stamped sheetmetal and have such thin walls that a good direct threaded engagementwith the pipe sections is ditlicult to secure. Where connecting bushingsof some sort are em- 6!, ploycd, a suliici'ently good mechanicalconnection is made between the pipe sections and the switch boxes, butthe electrical connection is very inferior. If the sheet metal of theswitchuhoxes is oxidized, as is the usual case, it may happen that thepipe is practically insulated from the boxes altogether. Under' thesecircumstances, a short on such pipe section would immediatelydangerously elevate its potential.

In carrying out my invention to overcome the foregoing diihculties, Imake use of the fact that the ends of the pipe sections,where theyjointhe switch or outlet boxes, are nec-. essarily threaded with usuai pipethreads. The ordinary pipe thread is slightly tapering or (:oniwl, whichfact has an important hearing in my invention. 1 provide stamped sheetmetal collars 3, of brass or copper with t alug ion one side.andinieriorly threaded at 5 to fit standard pipe threads. These collarswill, of course, be stamped in diil'ercnt sizes corresponding todifferent sizes of conduit piping ordinarily employed. They are mostconveniently punched. out of 3/16 or .1/4 sheet brass or copper, andthen merely interiorly threaded, whereupon they are ready to beassembled upon the threaded section of the pipe, without any furthermachining or finishing processes to insure perfect lit. The

lateral lug i should, however, be drilled with a hole 6 of sufficientsize to receive a stout copper wire, and the interior of this hole isconveniently tinned at 7 to facilitate soldering such copper wireintegrally to the lug.

The use and operation of the invention will be clear from the drawings.

It is merely necessary to assemble the collars 3 upon the threaded endsof the pipe sections 1 adjacent to the connections of these pipesections to the various outlet, switch and auction boxes. Short lengthsof copper Wire 8 are then soldered to the collars on opposite sidesofthe various boxes, thereby bonding the various p pe sections to- 0gether in a continuous low-resistance circuit.

At some point a pipe 9 may be driven into the 011ml, or otherwisearranged to make a manner as the various sections 1 arebond-' ed to oneanother. Each collar ma-kes aperfect electrical connection-with itspipesection, partly because it is of suflicientthickness. to make a goodthreaded engagement therewith, and partly because of the fact that itcan be screwed back upon the tapered threads of the pipe section as faras the strength of the workman will permit, brightening up the surfacesof the threads by the friction, and insuring a high pressureand 00delectrical contact-between the engagmg metallic surfaces. The bond wires8 be- 'ing soldered to the respective collars, make v a substantiallyperfect electrical connection therebetween, so that the entire conduitpipe length is bonded into a very "perfect low f "evcgees resistancegrounded circuit. capable of carrying off heavy current, without unduerise of potential at any point.

comprising an integral metal collar interiorly pipe threaded forengagement with a pipe end, the pipe thread by reason of its taperaffording especially good electrical ground 'eonnector for conduitWiring 25 connection between said collar and )ll)!...Stll(l collarfurther being provided with an integral laterally extending 111;; havinga lined aperture therein foiztlic reception of a connecting wire.

In Witness whereof, I subscribe my signa-. 3

